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EPoS |
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EPoS Contribution
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First ALMA Maps of Cosmic-Rays Ionization Rate in High-mass Star-forming Regions
Giovanni Sabatini INAF-Arcetri, Florence, IT | |
| Low-energy cosmic rays (<1 TeV) are a pivotal source of ionisation of the interstellar medium, where they play a key role in determining the chemical gas composition and, in turn, in influencing the formation of stars and planets. Observations of H3+ absorption lines in diffuse clouds - n(H2)~102 cm-3 - have been used for decades to provide reliable estimates of the cosmic ray ionisation rate relative to molecular hydrogen (ζH2). However, in denser clouds where stars and planets form, this method is often inefficient since H3+, similar to H2, does not emit rotational lines as it does not have a permanent electric dipole. The ζH2 estimates are therefore still provisional in this context, and represent one of the least understood ingredient when it comes to defining general models of star formation. Recently, a new analytical approach to estimate ζH2 in the densest regions of molecular clouds has been proposed based on observations of ortho-H2D+ as the main observational constraint to derive the amount of H3+. This has been applied in a large sample of high-mass star-forming regions. Exploiting the exceptional observational capabilities of ALMA, in this talk I will present the first high-resolution maps of ζH2 in two massive clumps. I will present these results and the way they provide crucial constraints for physical/chemical modelling of starforming regions. | |
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| Caption: Map of the log10(ζH2/s-1) derived for (a) AGAL351.571+00.762 and (b) AGAL354.944-00.537. The black contours show the ALMA continuum at 1.33 mm (levels: [3,6,9,15,30]σ). Cores' IDs ('c#'; in red) follow the classification defined by Redaelli et al. (2021). The figure is adapted from Sabatini et al. (2023). | |
| Collaborators: S. Bovino, Sapienza - URoma, IT E. Redaelli, MPE-CAS, DE |
Key publication
Relevant topic(s): Chemistry Cosmic Rays High-Mass SF |
| Relevant Big Question: Is the cosmic ionisation rate constant at the different scales of the star formation process? | |